This application claims priority to Korean Application No. 2002-0034788, filed on Jun. 21, 2002, which is incorporated in its entirety herein by reference.
This invention relates generally to the field of treating sewage/waste water using AI (artificial intelligence) for automatically controlling variable factors, and more particularly, a system and method using an AI control system for automatically controlling variable factors such as DO (dissolved oxygen), SRT (solids retention time) and others depending upon properties of inflow water, the internal condition of the reaction tank and a target treated water quality.
In conventional sewage/waste water treatment plants, each SP (set point) is personalized according to the experience of the operator considering a number of factors. Significant factors of the operator""s experience include seasonal differences in the temperature, BOD (biological oxygen demand) and stream flow of incoming fluids. The PID (proportional integral differential) and ON/OFF control system is implemented according to these factors. The operator changes each SP of DO and SRT for controlling the plant every several days based on daily data.
For example, in an automatic control system using the most commercialized PLC (programmable logic controller), data obtained from each measuring instrument is transmitted to the PLC. The data includes the BOD, incoming stream flow and water temperature, each DO of the first story and the second story of the exhalation tank, MLSS (mixed liquor suspended solids) of the aeration tank, a concentration of sludge, a drawn stream flow, and BOD of the outflow water for controlling each SP.
The data obtained from the input/output cards of the PLC (analog/digital (A/D) card, digital/analog (D/A) card, respectively) are operation-processed and PID and ON/OFF controlled through a central processing unit (CPU) with a small capacity and execution speed built into the PLC. Further, data inputted into and outputted from the PLC is transmitted to the computer through an interface via RS-232C communication signals.
The computer simply executes only the function to convert data inputted into and outputted from the PLC into data of a physical quantity (physical quantity data), which can be identified visually, displayed, saved and controlled.
The automatic control system implementing this method is simple, but it has difficulty in controlling DO and SRT using consecutive SPs depending on fluid properties of the inflow water. It is difficult to control each SP by applying changes that occur over time relying primarily on the operator""s intuition. Moreover, with this system, it is impossible to control each SP consecutively as a method to enhance the efficiency of treating sewage/waste water. In addition, in the absence of the operator, it is difficult to maintain the existing treatment efficiency or enhance the treatment efficiency.
One object of the invention is to overcome the disadvantages of the known systems and methods described above.
According to an embodiment of the invention there is provided a method for controlling treatment of sewage/waste water. The method comprises: measuring attributes of inflow water flowing into a sewage/waste water treatment plant, attributes of an internal condition of a reaction tank having a first story and a second story, and fluid present values (PVs) of efficiency attributes of outflow water; collecting data of the measured fluid PVs and operation-processing said data to convert said data into physical quantity data; obtaining each optimum set point (SP) of each dissolved oxygen (DO) and solids retention time (SRT) of the first story and the second story of an exhalation tank by comparing PVs of the measured attributes using a neural network control program with a back-propagation algorithm; converting each obtained optimum SP into an analog and digital control output value by comparing said each obtained optimum SP with each PV of each DO and SRT of the first story and the second story of the exhalation tank; and controlling each air control valve of the first story and the second story of the exhalation tank and a pump for drawing sludge based on each obtained control output value.
According to another embodiment of the invention there is provided a system for controlling treatment of sewage/waste water. The system comprises: measuring instruments for respectively measuring attributes of inflow water flowing into a sewage/waste water treatment plant, attributes of an internal condition of a reaction tank having a first story and a second story, and fluid present values (PVs) of efficiency attributes of outflow water; a computer for: collecting data of the measured fluid PVs, and operation-processing the data to convert the data into physical quantity data; obtaining each optimum set point (SP) of each dissolved oxygen (DO) and solids retention time (SRT) of the first story and the second story of an exhalation tank by comparing PVs of the measured attributes by means of an application program including a neural network control program using a back-propagation algorithm; and converting each obtained optimum SP into an analog and digital control output value by comparing each obtained optimum SP with each PV of each DO and SRT of the first story and the second story of the exhalation tank; and air valve controllers for controlling each air control valve of the first story and the second story of the exhalation tank and a pump for drawing sludge by using a control output value.
Further objects, features and advantages of the present invention will become apparent from the detailed description of preferred embodiments that follows, when considered together with the accompanying figures of drawing.